It seems to me you are being almost deliberately obtuse. Of course the brain has developed over the long course of evolution via sexual selection. The same process happens in parakeets. They have brains because they evolved brains. Some of that brain power went to making them better at catching prey, and some went to making them better mating-call singers, leading to larger brain size in the next generation. Humans just happen to be the brainiest of all creatures; but the mechanism is the same. You might as well argue that the “intelligence explosion” starts with the first prokaryote.
Ditto your argument about machines being used to improve machines. You know, cave dwellers used tools to improve their tools. Is that when the “intelligence explosion” began with recursion?
You are not even talking about the same topic that Eliezer is. I’m a low-ranking grunt in the rationalist army, and usually I just lurk here because I feel often feel out of my depth. But it’s frustrating to see the thread get jacked by an argument that has no real content.
The problem you are having is that all of your individual points are true as far as they go, but you’re just restating agreed-upon facts using some borrowed terms to make it sound grand and important. I suggest you re-read the posts Eliezer linked to about the “virtue of narrowness” and “sounding wise versus being wise.”
Now, back to my lurker’s cave.